Routing BGP (Internal BGP) di Juniper

Basic Knowledge

Peer ASs establish links through an external peer BGP session. As a result, all route advertisement between the external peers takes place by means of the EBGP mode of information exchange. To propagate the routes through the AS and advertise them to internal peers, BGP uses IBGP. To advertise the routes to a different peer AS, BGP again uses EBGP.

To avoid routing loops, IBGP does not advertise routes learned from an internal BGP peer to other internal BGP peers. For this reason, BGP cannot propagate routes throughout an AS by passing them from one router to another. To achieve an IBGP full mesh, you configure a direct peering session every host to every other host within the network. These sessions are configured on every router within the network, as type internal.

As a network grows, the full mesh requirement becomes increasingly difficult to manage. In a network with 1000 routers, the addition of a single router requires that all the routers in the network be modified to account for the new addition. To combat these scaling problems, BGP uses route reflection and BGP confederations. (Sumber)